This is a great site for recent information on the state of Education on the national level. It shows policies, recent activity, and a massive amount of information on all topics in education.
These is a website that provides quality educational resources. This website directs you to primary source documents that can be used for various activities or lessons. You can also buy various materials for teaching which are categorized by subjects.
This is a Smithsonian website that uses video and text to examine armed conflicts involving the U.S. from the Revolutionary War to the war in Iraq. This is a great tool to use when examining any war the U.S. has been involved in. This site also provides many activities.
This is an online reference for the Holocaust Museum located in Washington, D.C. It offers different kinds of activities and resources to use when teaching about the Holocaust.
An interesting activity put together by the NY Times that allows people to make certain choices in order to close the budget gaps that currently exist. Great for an economics class.
This site just has some general activities that you can do with your students if you are teaching about Greek mythology, and I think these would work well with other types of mythology too.